1. Field of the Invention
The present invention relates in general to tape drives, and in particular to a tape drive that can accept magnetic recording tapes of different widths.
2. Description of the Prior Art
Magnetic tape drives and magnetic tape cartridges are manufactured with standardized dimensions, conforming to an industry-wide form factor, so a standardized magnetic tape cartridge having a particular form factor can always be accepted in a drive designed for that form factor.
Data are magnetically recorded on a tape in adjacent tracks proceeding parallel to the longitudinal length of the tape. The access time to data that are stored at a location that is at some distance from one end of the tape is dependent on the time required to wind or unwind the tape to bring that particular location to a position in front of the read head. In order to reduce this access time, so-called wide tape cartridges have been developed in recent years, which have a tape width that is significantly larger than conventional standard magnetic recording tapes. For example, the standard ULTRIUM cartridge for the LTO drive operates with a tape that has a width of 12.7 mm. Increasing this width by 50%, while maintaining the same length of tape, would increase the storage capacity by 50% as well. Alternatively, if the width were increased by 50% but the total length of the tape were shortened, the same amount of data could be stored on such a tape as can be stored on the conventional, narrower tape, but the access time can be shortened due to the decreased tape length.
It is possible to achieve this increase in the tape width within the height (form factor) of a standard DLT cartridge, so that standard automation equipment can still be used. With this cartridge height, it is still possible to design the drive with the form factor known as 5¼″ Half Height.
This means that the standardized tape drive designed for this form factor would be able to receive and operate with a tape cartridge containing tape of the aforementioned narrower width, as well as with a different tape cartridge containing tape of the wider width. A problem associated with such interchangeable operation, however, is that the take-up reel in the tape drive must be designed to accommodate the widest tape width that will be used with the tape drive. This means that when tape of the narrower width is used, the internal dimension of the take-up reel (between the flanges) will be larger than the width of the narrow tape, and as the narrow tape is wound on such a reel, it will tend to meander or wander as it is wound on the hub. Precise alignment of the tape as it passes over the read/write head is important for accurate recording and reading of the data, because the data tracks are so closely packed together that a slight misalignment can cause data to be misread from the wrong track. Although the read/write head has tape guides disposed on opposite sides thereof, such guides operate by guiding the tape over a roller between two flanges, and the spacing between these two flanges must likewise be dimensioned so as to accept the widest tape. Such guides, therefore, would not be effective for accurately guiding the narrower tape.